Best Phase Change Materials for Flexible Heating/Cooling Membrane

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Discussion Overview

The discussion revolves around identifying suitable phase change materials for a flexible heating and cooling membrane that can endure extensive mechanical manipulation. Participants explore various materials that can effectively release latent heat over prolonged periods during the cooling phase, particularly focusing on their thermal properties and safety considerations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that magnesium nitrate hexahydrate could be a viable option due to its latent heat properties but expresses concerns about its toxicity and flammability.
  • Another participant questions the suitability of magnesium nitrate hexahydrate, arguing that its behavior upon heating and hydration differs from a typical phase change material and raises concerns about water management in a closed system.
  • A different viewpoint proposes that the magnesium nitrate hexahydrate could still function effectively if contained within a rubber matrix, allowing for a mini closed system where steam could condense back into water.
  • One participant recommends wax as a common phase change material at the desired temperature, noting the availability of various formulations with different melting points.
  • Another suggestion includes exploring esters of palmitic acid and other saturated fatty acid esters that remain liquid at slightly higher than room temperature.

Areas of Agreement / Disagreement

Participants express differing opinions on the viability of magnesium nitrate hexahydrate, with some supporting its use while others raise significant concerns. There is no consensus on the best phase change material, as multiple alternatives are proposed and debated.

Contextual Notes

Participants highlight the importance of thermal conductivity and capacity in selecting materials, but specific mathematical or empirical data to support claims are not provided. The discussion remains open-ended regarding the optimal material choice.

Who May Find This Useful

This discussion may be useful for researchers and engineers involved in materials science, thermal management, and the development of flexible heating and cooling systems.

martinl
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Hi All,

I'm working on a project that requires a flexible membrane be heated and cooled about 2000 times.

During the cooling process, I require the material give off heat for as long a period of time as possible. I figure a phase change material will have the highest heat capacity and give off its latent heat, over an extended period of time, while cooling at it's melting point.

So, I'm looking for a phase change material that I can imbed in a thin layer of silicon rubber to form the heat sink part of my membrane.

I considered magnesium nitrate hexahydrate (melting point 87 C), but fear that it is too toxic and flammable. The final membrane will be handled extensively and twisted and bent many times over its lifetime.

Could someone please give me some more suggestions of what else to try?
As many as possible (I may want to mix them to even out the heat transfer over the temp range)

Thanks a lot. over its lifetime.
 
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I am not sure magnesium nitrate hexahydrate would work. If one heats a hydrated salt and removes the water of hydration, the heat is generated when the dehydrated salt is rehydrated (as in heat of hydration). That is different from a phase change. Besdies, in a closed system, where would the water go?

It would seem one needs a material with a low thermal conductivity (which works against heat up, but allows for long slow release of heat) and high thermal capacity.

Hmmm. Interesting problem.
 
I'v pretty much given up on magnesium nitrate hexahydrate, but I think it would still work. The MNH would be completely surrounded by the rubber matrix, so the water would separate out and turn to steam (in a bubble inside the rubber), then as the substrate cools, the steam would condense to water and re-bond into the MNH - a mini closed system.
 
I think at that temperature, the most common material is wax. There are a wide variety of formulations for wax that can give different melting points. Try http://www.thomasnet.com/nsearch.html?cov=NA&which=prod&what=wax&navsec=search&heading=93001808" for manufacturers and more information.
 
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Try the various esters of palmitic acid. Find some that are liquid at slightly higher than room temperature. Some other compounds you might consider are, in a general class, saturated fatty acid methyl or ethyl esters, cholesteryl esters, rigid rod aromatic esters.
 

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